Plant for controlling delivery of pressurized fluid in a conduit, and a method of controlling a prime mover

ABSTRACT

A plant for delivering a fluid in a conduit (10) comprises a prime mover (2), for example a gas turbine, which is configured to drive one or more fluid delivery systems (34a-c, 35a1-c1, 35a2-c2) for delivering a fluid in the conduit (10). A first sensor (16) is configured for sensing pressure variations in the pipe (10) and is connected to a first controller (7). The first controller (7) is configured to provide control signals to control valves (36a-c, 37a-c) for at least one fluid delivery system and to a control system (4, 3) for the prime mover (2). One or more hydraulic pumps (9a-c) are configured to operate the fluid delivery systems and are driven by the prime mover, whereby interaction between the hydraulic pumps and the prime mover is controlled based on sensed pressure in the pipe (10).

RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. § 365 to International PCT Application No. PCT/NO2017/050307 filed Nov. 28, 2017, which claims priority to Norwegian Application No. 20161911 filed Nov. 30, 2016; the disclosure of each is incorporated herein in its entirety by reference.

FIELD OF THE INVENTION

Embodiments of the invention generally concern methods of controlling a prime mover which is configured to drive one or more fluid delivery systems for delivering a fluid in a conduit. This may be particularly useful in the extraction of shale oil and/or gas by means of pressure pumping equipment for well stimulation, commonly known as “hydraulic fracturing” or “fracking”, but is not limited to such operations.

BACKGROUND OF THE INVENTION

The majority of the equipment used for pressure pumping has been following the same principle for several decades: a trailer or truck mounted power pack (diesel-powered reciprocating engine, or a gas turbine engine) drives a pressure pump through a multi-speed transmission gear box. All parts are mechanically connected.

A typical pressure pump comprises two major parts: a “fluid end” and a “power end”. The fluid end is the actual pressure pump, pressurizing the fracturing fluid. It is normally a plunger/piston pump, typically operating at 150-300 strokes per minute, and is an exchangeable unit. The power end is part of the drivetrain, and it is connected to a multi-speed transmission. One of the primary functions of the power end is to convert rotational force to reciprocating force. The power end has a reduction gear box on the inlet, and is connected to the plunger on the fluid end via a crankshaft and a crosshead. The power is normally provided by a reciprocating engine, although gas turbine engines are also used.

Some of the problems associated with the prior art are shortened expected lifecycles of the equipment, as well as high maintenance costs during the lifecycle of the drivetrain. In addition, the prior art plants have a large surface footprint.

The prior art includes CN 104806220 A, which describes “fully-hydraulic driven” fracturing equipment with a power unit and a fracturing pump. The power unit comprises an engine unit, a transfer case unit, and a hydraulic pump unit. Three hydraulic pumps are installed on each transfer case, and the hydraulic pump unit is connected through hydraulic pipelines. The fracturing pump has a left and a right pump head, and three two-way hydraulic oil cylinders arranged in parallel are installed on the fracturing pump. The fracturing pump is driven by the two-way hydraulic oil cylinders so that the equipment power is increased, the equipment discharge flow is increased, and the equipment weight and size are reduced.

The prior art also includes CN 104727797 A and CN 204552723 U, which describe a system where an engine, a transfer case, a plurality of variable displacement plunger pumps, and a double-acting fracturing pump are arranged on a chassis. The output end of the engine is connected with the input end of the transfer case, and the output end of the transfer case includes a plurality of power take-off ports. Each power take-off port is connected with one variable displacement plunger pump. The plunger pumps drive the double-acting fracturing pump through a hydraulic system.

The prior art also includes CN 104728208 A, which describes a high-power hydraulic driving fracturing-pump pump station system, in which the hydraulic cylinders are connected with the fracturing cylinders. An electric motor driven hydraulic pump provides high-pressure oil, and a fluid outlet, manifold outputs a high-pressure fracturing fluid.

The prior art also includes CN 104453825 A, which describes a modularized fracturing pump set which has a power unit and a fracturing pump unit. An auxiliary engine is arranged on the power unit and is connected to a hydraulic pump. A torque converter is arranged in the fracturing pump, and the input end of the torque converter is connected to the main engine. The output end of the torque converter is connected to a gearbox, and the output end of the gearbox is connected to the fracturing pump.

The prior art also includes WO 2014/078236 A1, which describes a turbo-shaft engine having a drive shaft and a high pressure (and high-RPM) centrifugal pump coupled to the drive shaft.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the disclosure in order to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is not intended to identify critical elements of the disclosure or to delineate the scope of the disclosure. Its sole purpose is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description that is presented elsewhere.

According to an embodiment, a plant for controlling delivery of a pressurized fluid in a conduit includes a prime mover, a sensor, and a first controller. The prime mover is configured to supply torque to one or more hydraulic pumps, and each hydraulic pump is configured to supply hydraulic pressure to a respective positive displacement fluid delivery system via respective control valves. Each positive displacement fluid delivery system is configured to deliver the pressurized fluid in the conduit. The first sensor is configured for sensing pressure variations in the conduit, and the first controller is in data communication with the first sensor. The first controller is configured to provide control signals to the control valve for at least one of the fluid delivery systems and to a control system for the prime mover.

According to another embodiment, a plant for controlling the delivery of a pressurized fluid in a conduit is characterized by a prime mover which is configured to supply torque to one or more hydraulic pumps, each hydraulic pump configured to supply hydraulic pressure to respective positive displacement fluid delivery systems, each positive displacement fluid delivery system configured to deliver said fluid in the conduit, a first sensor configured for sensing pressure variations in the conduit and connected to a first controller. The first controller is configured to provide control signals to the control valves for at least one fluid delivery system and to a control system for the prime mover.

In an embodiment, the plant has one or more hydraulic pumps driven by the prime mover. The hydraulic pumps are configured to communicate with a controller to operate the fluid delivery systems. Interaction between the hydraulic pumps and the prime mover is controlled based on sensed pressure variations in the conduit.

In an embodiment, the plant further includes valve outlet feedback pressure sensors connected to respective control valves, and a valve inlet pressure sensor connected to the control valve. The plant may further include a valve controller configured for receiving signals from the pressure sensors and the first sensor and position feedback from the positive displacement fluid delivery systems. The valve controller is configured for providing control signals to the control valves.

In an embodiment, the prime mover is a gas turbine engine and a gear unit is arranged between the gas turbine engine and the hydraulic pump.

In an embodiment, the prime mover is a reciprocating engine.

In an embodiment, at least one positive displacement fluid delivery system includes a positive displacement pump.

In an embodiment, the plant is positioned on a trailer.

According to still another embodiment, a method is provided for controlling a prime mover which is configured to drive one or more positive displacement fluid delivery systems for delivering a fluid in a conduit. The method is characterized by sensing the pressure variations in the fluid in the conduit and, based on the sensed pressure variations, controlling at least one of the positive displacement fluid delivery system and controlling the power output of the prime mover.

In an embodiment, the method includes determining an estimated power consumption.

In an embodiment, the method includes controlling the prime mover fuel supply based on variations in sensed pressure.

In an embodiment, at least one positive displacement fluid delivery system is controlled based on a set-point identified and set by an operator or an overall control system.

In an embodiment, a first controller provides control signals to hydraulic pumps that are configured to operate the fluid delivery systems and that are driven by the prime mover, whereby the interaction between the hydraulic pumps and the prime mover is controlled based on sensed pressure variations in the conduit.

Although embodiments of the invention are particularly useful in hydraulic fracturing (“fracking”) operations, embodiments may also be applicable for all positive displacement pumping processes in which control is based on at least one of: flow measurements, pressure settings, and feedback pressures. The invention shall therefore not be limited to fracking operations unless such is specifically claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates one embodiment of a plant for controlling delivery of pressurized fluid in a conduit, in accordance with an embodiment of the current invention.

FIG. 2 is a perspective view of a mobile embodiment of the plant of FIG. 1, in a transportation configuration.

FIG. 3 is a perspective view of the mobile embodiment of FIG. 2, in a pumping (operational) configuration.

FIG. 4 is a perspective view of the mobile embodiment of FIG. 3, shown with the housing removed for illustration.

DETAILED DESCRIPTION OF AN EMBODIMENT

The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, “upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader's convenience only and shall not be limiting.

Referring initially to FIGS. 2, 3, and 4, the invented plant is in this illustrated embodiment arranged as a mobile unit 18 on a trailer 19 and enclosed by a housing 20. Doors in the housing provide access to the plant, and rear doors may allow the movable unit comprising fluid end 21 with its double-acting cylinders 22 to be moved out and down (see FIG. 3) when the plant is in operation. Pipes 21 a are configured for connection to well piping (not shown).

Referring to FIG. 4, the mobile plant in the illustrated embodiment includes a gas turbine 26 connected via a duct 27 a to an air inlet 27, and also connected to an exhaust opening 26 a. The gas turbine 26 receives fuel from a fuel tank 32. Supply lines and hoses, power lines and control lines, etc., are not shown, as these components are commonly known in the art.

The gas turbine 26 is connected to a set of single or tandem-mounted hydraulic pumps 30 via a gearbox 28. Reference numbers 31 and 29 denote a hydraulics tank and accumulator tanks, respectively. Louvers and air filtration container 23 is arranged towards the rear of the mobile unit, behind oil cooler gearbox 25 and hydraulics cooler 24.

The hydraulic pumps 30 operate hydraulic cylinders 22 in the plant's fluid ends 21. Each hydraulic cylinder operates one plunger, in each of the plant's two fluid ends 21.

A typical configuration of the invented plant will now be described with reference to the diagram in FIG. 1.

In FIG. 1, three systems are shown—denoted A, B, C, respectively. It should be understood that only system C is illustrated in detail in FIG. 1, for clarity of illustration. The skilled person will understand that the components and functions illustrated and described with reference to system C also can be applied to systems A and B. It should also be understood that the invention shall not be limited to the number of systems shown in FIG. 1.

Reference number 1 denotes a power source having a prime mover 2. The prime mover 2 may be, for example, a gas turbine engine or a reciprocating engine, controlled via a throttle 3 (controlling fuel supply F and receiving information regarding rotation speed R). The prime mover 2 is connected, and configured to transfer torque T, to a gear unit 8. The gear unit 8 transfers torque T‘ to individual hydraulic pumps 9 a-c, and each pump has respective pump pressure sensors 13 a-c.

If the prime mover 2 is a gas turbine, the gear unit 8 may be configured to reduce high-rpm output from the turbine. If the prime mover is of another type of engine (e.g. a reciprocating engine), the hydraulic pumps may be driven directly by the engine, and the gear unit 8 may be omitted.

Each hydraulic pump 9 a-c supplies hydraulic pressure to respective positive displacement fluid delivery systems (in the illustrated embodiment, double-acting hydraulic cylinders 34 a-c) via respective control valves 36 a-c, 37 a-c. A reservoir tank 11 and a cooler 17 are fluidly connected between the hydraulic pump 9 c and the control valves 36 c, 37 c. The circuit also comprises an accumulator 33 for mitigating pressure pulses.

Each hydraulic cylinder 34 a-c is operably connected to respective sets of fluid plungers 35 a 1-c 1, 35 a 2-c 2. The fluid plungers 35 a 1-c 1, 35 a 2-c 2 force fluid to the well via the fluid supply line 10. The invention shall, however, not be limited to such fluid plungers. Reference number 12 denotes a supply line from a fluid blending system.

Well feedback pressure sensor 16 is connected to, and configured to sense the pressure in (and hence pressure variations in) the supply line 10. Valve outlet feedback pressure sensors 15 are connected to respective control valves 36 c, 37 c. Valve inlet pressure sensor 14 is connected to control valve 36 c. A valve controller 7 (typically a programmable logic controller—PLC) receives signals from the pressure sensors 14, 15, 16, position feedback Cp from the hydraulic cylinders, and provides control signals Vf to the control valves 36 c, 37 c.

A main control system 4 controls the throttle 3 based on power request Pr and provides power feedback Pf. The main control system 4 also receives transport security interlock feedback Ts from the gear unit 8, and estimated power consumption data EPC from the PLC 7, based on the sensed pressure variations by well feedback pressure sensor 16. A louver controller 5 is also in communication with the main control system 4, to open and close louvers (for e.g. ventilation and fire control). The main control system 4 receives data from a hydraulic pump controller 6 (e.g. a PLC) and provides a power command Ac to the hydraulic pump controller 6. The hydraulic pump controller 6 in turn provides the required displacement command Dc to the hydraulic pump 9 c based on pump pressure feedback Pp (from the pressure sensor 13 c). The main control system 4 also provides data regarding requested cylinder speed RCS to the valve controller 7, which in turn determines and provides the valve flow control signal Vf to the control valves 36 c, 37 c, as described above.

The plant thus includes a hydraulic-pressure/flow-controlled power transmission, in which all power from the prime mover is transformed into hydraulic power by the hydraulic pumps. The hydraulic pumps enable the prime mover to start against little or no load, and the hydraulic pumps may start the positive displacement fluid delivery system under varying load conditions.

When the plant is in use in a fracking operation, the prime mover 2 and the hydraulic pumps 9 a-c operate the hydraulic cylinders 34 a-c and fluid plungers 35 a 1-c 1, 35 a 2-c 2 to supply pressurized fracturing fluid to the line 10 (and thus the subterranean well). The hydraulic fracturing pressure generated in the well is a result of the well pressure and the hydraulic pressure generated by the plungers. The well pressure (which is sensed by the sensor 16) is communicated to the valve controller PLC 7, which controls the control valves 36 a-c, 37 a-c and also determines the estimated power consumption EPC, which is transmitted to the main control system 4. The prime mover fuel supply (e.g., turbine fuel injection) may thus be governed by the well pressure, or rather the variations in pressure, as sensed continuously by the sensor 16. The turbine fuel control receives pressure reading from the hydraulic control system, based on the pressure and rate reading from the hydraulic fracturing pressure. The hydraulic control system then performs a control action based on a set-point (rate/pressure) identified and set by the operator.

The delay which is inherent in hydraulic components, or which may be provided (controlled) by the main control system 4, provides sufficient time for the turbine fuel control to predict what is going to happen, and take action before it happens.

This means that the prime mover can—before the requirement arises—either increase the fuel injection (open throttle) to be ready for higher demand from the hydraulic pumps, or lower the fuel injection (restrict throttle) to adapt to the estimated future requirement of torque, and thereby accommodate the change in rate/pressure. This function may be particularly useful in embodiments where the prime mover is a gas turbine engine, as such turbines normally operate at high rotational speeds, and have low torque. The control system may in this fashion prevent the gas turbine engine from over-speeding, and further give the gas turbine engine a head-start on a predicted increase in torque demand.

When the requirement for fracturing fluid in the well changes, or actual consumption of fracturing fluid is changing and not complying with the set point as set by the operator or as determined by an overall control system, the valve controller 7 and pressure sensor 16 are sensing this, based on sensed pressure variations. The set point may also be defined based on a prioritized list, defined by an overall control system, of how deviating conditions are to be handled. Based on rate/pressure difference between the set point and the actual pressure reading (as sensed by 16), there will occur a situation that the actual power command Ac (fed to main controller 4 by the pump controller 6) differs from (less or more) the estimated power consumption EPC (fed to the main controller 4 by the valve controller 7). This will lead to a situation where the main controller 4 will be able to give appropriate control signals, and be able to control the instant in which the control signals are given, to both the pump controller 6 and to the prime mover throttle control 3—whether simultaneously or at a controlled difference to have the prime mover act in a predictive manner.

Although an embodiment of the invention has been described with reference to three hydraulic pumps, it should be understood that other embodiments may utilize fewer or more hydraulic pumps.

Although an embodiment of the invention has been described with reference to a mobile unit, it should be understood that other embodiments may be formed as a stationary plant.

Although an embodiment of the invention has been described with reference to driving fluid ends (double-acting hydraulic cylinders), it should be understood that other embodiments may utilize other pumping principles driven by hydraulic flow and pressure, i.e. positive displacement pumps. The invention shall thus not be limited to the double-acting hydraulic cylinders.

Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present disclosure. Embodiments of the present disclosure have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present disclosure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. The specific configurations and contours set forth in the accompanying drawings are illustrative and not limiting. 

1. A method of controlling a plant for delivering a pressurized fluid in a conduit, the plant comprising: a prime mover configured to supply torque to one or more hydraulic pumps, each hydraulic pump being configured to supply hydraulic pressure to a respective positive displacement fluid delivery system via a respective control valve, each positive displacement fluid delivery system being configured to deliver the pressurized fluid in the conduit; a first sensor configured for sensing pressure variations in the conduit; and a first controller in data communication with the first sensor, the first controller being configured to provide control signals to the control valve for at least one of the fluid delivery systems and to a control system for the prime mover; the method comprising: sensing pressure variations in the pressurized fluid in the conduit; and based on the sensed pressure variations: (a) controlling at least one of the positive displacement fluid delivery systems; and (b) controlling power output of the prime mover.
 2. The method of claim 1, further comprising determining an estimated power consumption.
 3. The method of claim 2, wherein controlling power output of the prime mover comprises controlling a fuel supply of the prime mover.
 4. The method of claim 3, further comprising controlling the at least one positive displacement fluid delivery system based on a set-point, the set-point being identified and set by an operator or an overall control system.
 5. The method of claim 4, further comprising: the first controller providing control signals to the one or more hydraulic pumps; and controlling interaction between the hydraulic pumps and the prime mover based on sensed pressure variations in the conduit.
 6. The method of claim 1, wherein the control valve for at least one of the fluid delivery systems is a plurality of control valves.
 7. A plant for controlling delivery of a pressurized fluid in a conduit, the plant comprising: a prime mover configured to supply torque to one or more hydraulic pumps, each hydraulic pump being configured to supply hydraulic pressure to a respective positive displacement fluid delivery system via a respective control valve, each positive displacement fluid delivery system being configured to deliver the pressurized fluid in the conduit; a first sensor configured for sensing pressure variations in the conduit; and a first controller in data communication with the first sensor, the first controller being configured to provide control signals to the control valve for at least one of the fluid delivery systems and to a control system for the prime mover.
 8. The plant of claim 7, wherein: the one or more hydraulic pumps are each configured to communicate with a hydraulic pump controller and a valve controller and to operate the fluid delivery systems; the one or more hydraulic pumps are each driven by the prime mover; and interaction between the one or more hydraulic pumps and the prime mover is controlled based on sensed pressure variations in the conduit.
 9. The plant of claim 8, further comprising: valve outlet feedback pressure sensors connected to respective control valves; and a valve inlet pressure sensor connected to a respective control valve.
 10. The plant of claim 9, wherein the first valve controller is configured for: receiving signals from the first sensor, the valve outlet feedback pressure sensors, and the valve inlet pressure sensor; receiving position feedback from the positive displacement fluid delivery systems; and providing the control signals to the control valves.
 11. The plant of claim 10, wherein the prime mover is a gas turbine engine.
 12. The plant of claim 11, further comprising a gear unit arranged between the gas turbine engine and the hydraulic pump.
 13. The plant of claim 10, wherein the prime mover is a reciprocating engine.
 14. The plant of claim 10, wherein at least one of the positive displacement fluid delivery systems comprises a positive displacement pump.
 15. The plant of claim 10, further comprising at least one trailer; the prime mover, each hydraulic pump, and each positive displacement fluid delivery system being positioned on the at least one trailer.
 16. The plant of claim 7, further comprising: valve outlet feedback pressure sensors connected to respective control valves; and a valve inlet pressure sensor connected to a respective control valve.
 17. The plant of claim 7, further comprising: a respective valve outlet feedback pressure sensor connected to each control valve; and a valve inlet pressure sensor connected to a respective control valve.
 18. The plant of claim 7, wherein the prime mover is selected from the group consisting of: a gas turbine engine, a reciprocating engine, and an electric motor.
 19. The plant of claim 7, wherein at least one of the positive displacement fluid delivery systems comprises a positive displacement pump.
 20. The plant of claim 7, further comprising at least one trailer; the prime mover, each hydraulic pump, and each positive displacement fluid delivery system being positioned on the at least one trailer.
 21. The plant of claim 7, wherein the control valve for at least one of the fluid delivery systems is a plurality of control valves. 